Multiple operation mode road vehicle control system



July 20, 1965 J. B. BRENNAN 3,195,672

MULTIPLE OPERATION MODE ROAD VEHICLE CONTROL SYSTEM Filed April 29, 1963John B. Brennan His Afiorney United States Patent 3,195,672 MULTIFLEOPERAHON MGDE ROAD VEHZCLE CUNTRQL SYTEM John B. Brennan, Flint, Mich,assignor to General M0- tcrs Corporation, Detroit, Mich a corporation ofDelaware Filed Apr. 29, 1963, der. No. 276,318 Claims. (Cl. 183-823) Theinvention relates to a control system for a road vehicle and moreparticularly to one in which several different modes of operation areselectively available. A system embodyin the invention can be set by thevehicle operator so that the entire system is inoperable in onecondition, a second condition in which the system will warn the vehicleoperator of the attainment of a desired vehicle speed and may uponfurther selection by the vehicle operator control the road speed of thevehicle so as to maintain it at the desired set speed; a third conditionin which the system is so energized as to permit the operator toaccelerate the vehicle to the set speed under power throttle control andto maintain the set speed only so long as the operator positivelymaintains the acceleration control in position; a fourth condition inwhich the system is prearrned so that when the vehicle is manuallyaccelerated to the set speed the system automatically talres overcontrol of the vehicle speed and maintains the set speed; and a fifthcondition combining the features of the third and fourth conditions.

The system embodying the invention is somewhat similar to the systemsdisclosed and claimed in copending applications Serial No. 211,763,filed Euly 23, 1962, and en- 'tled Vehicle Speed Warning and CruiseControl System, now Patent No. 3,109,507 and Serial No. 276,317, filedApril 29, 1963, and entitled Vehicle Road Speed Warning and SpeedControl System. The system also utilizes the speed transducer disclosedin copending applications Serial No. 67,820, filed November 7, 1960, andentitled Vehicle Speed Warning and Cruise Control System, now Patent No.3,088,538 and Serial No. 137,423, filed September 11, 1961, and entitledVehicle Speed Naming and Cruise Control System, now Patent No.3,087,340. Reference is therefore made to these applications for detailsof construction and operation of the speed transducer and thedisclosures therein relative to the speed transducers are incorporatedherein by reference.

A system embodying the invention herein disclosed and claimed isdesigned to give a complete range of operational choices to the vehicleoperator, depending upon the condition of operation of his vehicle andhis personal desires. The system includes a condition selection switchassembly, a speed transducer into which is set a desired speed which iscompared to the actual vehicle speed and, within a constant range ofvehicle speed, senses s eed error and generates a speed error signal.This signal is translated into a fluid pressure signal which acts on aservo attached to the vehicle engine throttle valve linkage to eithergive a speed warning condition of operation or a speed maintainingcondition of operation or to accelerate the vehicle to the set speed,depending upon the selected condition and the mode or" operation withinthat condition chosen by the vehicle operator. The system includes abrake release switch which deenergizes the system when the vehiclebrakes are applied. it also includes a mode switching valve arrangementfor selectively admitting a fluid pressure into the throttle valvecontrolling servo to oppose the proportional control fluid pressure forspeed maintenance or to accelerate the vehicle to the set speed,depending upon the selected condition of operation. The system includesmechanism for inhibiting the accomplishment of a speed maintainingcondition of operation until the vehicle is manually accelerated intothe speed error 3,l5,h?2 Patented July 2%, 15965 sensing range. Thecontrols for the fluid pressure portion of the system are preferablyelectrical to permit ease of assembly within a vehicle.

In the drawing:

The figure is a schematic diagram of the system embodying the inventionas installed on a vehicle having an engine controlled by the throttlevalve. Mechanical por tions of the systems are illustrated in section asnecessary, with parts being broken away, and with other portions of thesystem being illustrated as block diagram sections.

The vehicle in which the system shown in the drawing is installedincludes an accelerator pedal it connected to move an engine throttlevalve 12 through a rod 14 and an arm 16 in the usual manner. A throttlevalve return spring 18 is provided to urge the throttle valve 12 to thezero throttle position. The vehicle is also equipped with a brake pedalarm 20 which is pivoted in the usual manner when the operator desires toactuate the vehicle brakes.

A speed transducer assembly 22, which may be of the type disclosed inthe above noted applications, receives vehicle speed information throughthe speedometer cable 24. A desired vehicle speed is set into the speedtransducer 22 through the cable it: which is actuated by the speed setknob 28 under control of the vehicle operator. The speed transducer 22includes the speed error sensing mechanism 3% which is schematicallyillustrated as having a switch 32 therein. This switch is normallyclosed until the actual vehicle speed enters a constant range of vehiclespeed containing the desired set speed, at which time the contacts ofthe switch 32 are cyclically opened and closed with the amount of opentime in each cycle depending upon the speed error so that the resultingsignal reflects the amount of speed error and indicates whether thespeed error is above or below the set speed. Details of operation ofspeed transducers of this type are found in the above notedapplications. The speed transducer 22 has one contact of switch 32grounded at 34 and the other contact connected to a resistor 3a? throughelectrical lead 33. A second resistor 4% is connected in series withresister as by electrical lead 42 and an electrical lead 44 connectselectrical lead 42 to the base of the transistor 4-5. The collector sideof the transistor 46 is connected to ground and the emitter side isconnected to electrical lead 4-8. Resistors 36 and 46 provide a voltagedivider and the arrangement is such that when current is flowing throughthe switch 32 the transistor 46 is on and when switch 32 is opened thetransistor is off.

The system also includes the servo assembly 50. The servo housing 52 isdivided into a speed control chamber 54 and a speed warning chamber 56by the power diaphragrn 58. Push rod as is connected to the diaphragm 58and extends through seal 62 in the housing. Push rod 6% is connectedthrough joint 64 and the lost motion mechanism as to the throttlelinkage arm 16 by a pin and slot connection 68. Movement of diaphragm 53to the left can urge the throttle valve 12 toward the open throttlevalve position and movement of the diaphragm to the right can urge thethrottle valve to the closed throttle valve position.

A proportional control mechanism 743 is provided in the portion of servohousing 52 adjacent chamber ss. Mechanism 79 includes an electromagnet72 having a coil 74 and a core '75. A passage 78 extends through core'76 and is connected to a fluid pressure conduit till at one end andterminates in a valve seat 82 within chamber 5%. Conduit St; isconnected with a conduit 84 in conununication with a suitable source offluid pressure such as the engine intake manifold 86. A valve assembly88 is pivotally mounted on support lid in chamber 56 so that the valve$2 of the assembly 83 is in position to seat and unseat relative to thevalve seat 82 as the valve assemblyds pivoted on support @tl. Anothervalve 94 mounted on the own 'switch subassembly at the same time.

other side of the pivot from valve 92 is positioned to open and close anatmospheric air inlet orifice 96 connected with the atmosphere throughinlet 98. Spring 1% urges the valve assembly to a pivoted positionwherein'valve '94 closes orifice 96 and valve 92 opens passage 78 tochamber 56. Electromagnet 72 has one end connected through electricallead 162 to resistor of the speed transducer assembly 22. The other endof coil 74 is conhec'tedwith electrical lead 48 whichis connected withthe emitter side of transistor 46.

An inhibiting and prearming switch 164 includes a nonmagnetic andelectrically insulating housing 1% having a diaphragm 108 dividing thehousing into an atmospheric housing 1-06. Spaced'contacts and 122 aremounted in housing'lilti so that they are in position to be contacted bybar 116 and'cooperate therewith to form an electrical switch whichisclosed when subatmospheric pressure is imposed in chamber 112 ofsufficient pressure dilterential to move the diaphragm 1138 downwardlyagainst the magnetic force of magnet 11S acting on bar 116. Electricallead 124 is electrically connected to contact 120 and electrical lead126 is electrically connected to contact 122.

A mode control valve assembly 128 includes a housing 130 provided withan inlet passage 132 and an outlet passage 134 connected through valveseat 136 and controlled by valve 138. Passage 132' is connected throughconduit 140 to the intake manifold conduit 84 and passage 134 isconnected through conduit 142 to the speed control chainber'54 of theservo 50. Valve 138 is normally held seated against seat 136 by spring144. An electrom'agn'et 146 is mounted 'on housing 13) and includes a Icoil 148 and a movable core 151 which is connected to i valve138 throughthe aperture 152. The electromagnet housing 154 is provided with airinlet aperture'156 so that atmospheric air is present in passage 134 byway of j aperture 152 when valve 138 is seated on valve seat 136.

One end of core also acts 'as a valve to close air inlet 156 when theelectromagnet 146 is electrically energized to move core 150 upwardly,thus sealing passage 134 from atmospheric pressure under this condition.When valve 138 is unseated in this manner, passages 132 and 134 areinterconnected. Coil 1 18 has one end connected to ground throughelectrical lead 158 and theother end connected to electrical'lead 160.

'A mode selector switch assembly 162 is provided with four switchsubassemblies 164, 166,163 and 170. Each switch subassembly includes acontact arm, 172, 174, 176

and 178, respectively, and five contacts which are identi' tied in eachswitch assembly as contacts F, N, A, B and P, in order. Arms 172,174,176 and 178are connected by an actuating rod 189 so that they move inunison andeach arm contacts the same named contact in its Theassembly162 may easily be constructed as a rotary type switch assemblyrather than as the linear movement type schematically illustrated. Arm172 is grounded through lead 182. Arm 174 is connected to electricallead 134. Arm 176 is connected to electrical lead 186. Arm 178 isconnected to electrical lead 188. In the position shown in the drawingeach of the arms is in contact with contact N of its switch subassembly.The position of the arms in'relation to the contacts of each switchsubassembly correspond to the five mode selector positions indicated bythe pointer 190 on rod 186. These conditions are Otf, Normal,Accelerate, Both and Prearm. A'knob 192 is secured to rod 180 so thatthe rod may be moved to any one of the five positions.

An operational control switch assembly 194 includes switches 19 6 and198. Switch 196 is comprised of conl tacts 21th and 202 which arenormally bridged by bar 20 Switch 198 includes contacts 206 and 208which may be bridged by bar 210. Spring 2112 keeps switch 198 normallyopen and spring 213 keeps switch 196 normally closed. Bars 204 and 211are mounted on a push-pull rod 214 which extends through the speed setknob 28 and is provided with a knob 216 by which the operator cancontrol the switch. An abutment 218 on rod 214 is provided to engage bar234 so that upon pulling knob 216 to the left, the operator can openswitch 196. In the position shown, spring 212 is almost at its freelength so that abutment 213 is normally spaced from bar 204 and the bar2124 is normally engaged with itscontacts.

A brake switch'assembly 224 is mounted on the vehicle so that itscontact 222 engages its contact 224 when the brake pedal arm 29 is in'thebrake release position. Spring 226 normally holds contact 222against contact 224. A switch operating arm 228 is secured to contact222 and is operated by the brake pedal arm pin 230 to open the switch220 when the brake is applied.

A holding relay assembly 232 includes an electromagnet 234 which has oneend of its coil 236 connected to ground through electrical lead 238 andthe other end connected to electrical lead 126. A relay armature 2419 ispivoted at 242 and biased by spring 244 away from the core 246 ofelectromagnet 234. Armature 24% acts as an actuating lever to whichcontact mounting springs 248 and 250 are attached in electricallyinsulated relation. Normally open switches 252 and 254 have contacts 256and 258 respectively secured to springs 248 and 250 and cooperatingcontacts 260 and 262 which are respectively engageable by contacts 256and 258 when electromagnet 234 is energized to pivot armature 2 3d. Thesystem is energized by means of a suitable sourc of electrical energyschematically illustrated as battery 264. The battery is connectedthrough ignition switch'266 to electrical lead 263. This lead iselectrically connected to contact 222 of the brake switch 228 and tolead 102 intermediate resistor 49 and the'electromagnet 72. Contact 224of the brake switch 220 is connected through electrical lead 270 tocontacts N, A, B and P of switch 179.

.Contact 202 of operational control switch assembly 194 is connectedthrough electrical lead 272 to contacts B and P of switch 168.Electrical lead 274 is connected to lead 272 and to contact 260 of theholding relay assembly 232. Contact 293 of operational control switchassembly 194 is connected to electrical lead 184'leading to arm 174 ofswitch 156 and is also connected through branches of this lead tocontacts N and A of switch 168. Contacts 200and 2136 are connected inparallel to'elec- I trical lead 188 which contains a transmissionoperated switch 282. This switch is closed only when the transmission isin the drive position, and may be omitted if it is not desired to renderthe systems inoperable in all other transmission control conditions.Electrical lead 276' is connected to contacts A and B of switch 166, tolead from electromagnet 146 of the mode'control valve assembly 128, andto contact'262 of the holding relay assembly 232. Contact F of switch164 is connected through electrical'iead 278 to electrical lead 48intermediate transistor 46 and electromagne't 72. Electricallead 186from switch arm 176 is connected to electrical lead 124 of theinhibiting and'prearming switch assembly 104. Contacts-256 and 258 ofholding relay assembly 232 are electrically connected at 281 to lead 126intermediate electromagnet 23 iand switch assembly 1194. Switch 164-therefore has open contacts N, A, B and P; switch 166 has open contactsF, N and P; switch 168 has open contact F; and switch 171 has opencontact F( V a The system may be conditioned for several diiterent typesof operation including one condition whereinthe entire system isinoperative. V The inoperative condition is obtained by settingindicator 1% of mode selector assembly 162-:at the Off position. Thecontact arms of each of the switches of assembly M2 are then in contactwith their associated contacts F. Thus switches 165, 163 and 17% areopen and electrical lead 278 is grounded through switch 16 This groundsboth the emitter and collector sides of transistor 46 so that coil '74of electromagnet 72 is always energized even though the vehicle mayenter the speed error sensing range. Thus valve )2 is held seated onseat 82 while valve @4 is open, and atmospheric air pressure is in speedwarning chamber 56. Since elcctromagnet 146 is deenergized, valve 136 ofthe mode control valve assembly 128 is seated and stares pheric air ispresent in the speed control chamber se of the servo 5t) throu h conduit142 and assembly 12.8. The openator therefore controls the enginethrottle valve 12 manually by movement of the accelerator pedal 1%? anddiaphragm 53 of the servo St? merely follows movements of the throttlelinkage.

When the operator positions indicator 1% in the Normal position, thecontact arms of the switches of selector assembly 162 engage theirassociated contacts N. Thus switch 3164 is open and transistor 46 is nolonger grounded through lead 278. Switch 166 is also open, whileswitches 168 and 176 complete circuits insofar as the switchesthemselves are concerned. Electrical energy from the source 264 goesthrough lead 263, brake relay switch 229, lead 276, switch 17%, lead 188and switch 223.2, to contacts 2th and 235 of operational control switchassembly 1194. Since switch'19fi is closed, lead 2.?2 is also energizedas is lead 274 to contact 26 19 of the relay assembly 232. When thevehicle is below the speed error sensing range the speed transducerswitch 32. is closed so that the tnansistor 4d completes the circuitcontaining lead 48 and coil 74 of elec-trornagnet 72 is thereforeenergized. Thus, as before, atmospheric pressure is in speed warningchamber 56 of the servo 58. Since electromagnet 146 is not energized,atmospheric pressure is also present in speed control chamber 54 of theservo. Due to the magnetic attraction of magnet 138, the switch Hi4 isopen. Since the electromagnet 23d of relay assembly 232 is alsodeenergized, switches 252 and 254 of that assembly are open.

When the vehicle reaches the lower limit of the speed error sensingrange switch 32 cyclically opens as described above. Coil 7i is thendeenergized while switch 32 is open, and vacuum from manifold 86 isproportioned into chamber 55 by valve 92 in accordance with the speedtransducer generated speed error signal. When the vehicle has reachedthe set speed, which may for example be mph. with the speed errorsensing range extending from 57 mph. to 63 mph, suihcient proportionedpressure at less than atmospheric pressure is im posed in chamber 56 tocause diaphragm 58 to move to the right and exert a throttle closingforce on arm 16 of the throttle linkage. This force is felt by thevehicle operator through the pedal ll as a back pressure. The forcebecomes stronger as the speed of the vehicle continues to increase untilthe vehicle passes beyond the speed error sensing range, at which timethe force is constant in relation to engine vacuum. When theproportional pressure in chamber 56 is sufficient to act on diaphragm138 of switch assembly 1% to move bar H6 away from magnet 1118, switch1M- is closed by engaging bar with contacts 129 and 12.2. This may occurat or slightly below the set speed. This does not energize electromagnet146 at this time since switch 198 of the operational control switchassembly 194 is open. However, the closing of switch assembly 1&4 uponsubstantial attainment of the set speed removes the inhibition of thesystem from being engaged in a speed maintaining condition of operation.After switch we is closed the operator may engage the system in thespeed maintaining condition of operation by pushing knob 216 inwardly toclose switch 193. This energizes electromagnet 234 through lead 184,switch 163, leads 336 and switch amt, lite and lead 12%. Thus the relayassembly 232 is actuated to close switches 252 and 254 and lead 276 isthereby energized through switch 254. Electromagnet M6 is then energizedthrough lead 169 to open valve 133 and admit manifold vacuum to speedcontrol chamber 54. The opposing engine intake manifold pressure andproportional control pressure act on diaphragm 53 to maintain thevehicle at the set speed. Since switch 252 is closed, electromagnet 2%remains energized through switch 1%, lead 272, lead 274, switch 252 andconnection 28% to lead 126. The operator may then release knob 216 andspring 212 will open switch 19-3. However, the holding relay assembly232 will hold electromagnet 14d energized and the system will remain inthe speed m-antaining condition of operation until released. The systemmay be released by actuating the vehicle brakes to open switch 22%, thusinterrupting the supply of electrical energy to electromagnet 1% cuttingotl the supply of vacuum to servo speed control chamber 54 and replacingit with atmospheric pressure. The same effect may also be obtained bypulling out knob 216 to open switch 1%, or moving knob 1% to repositionselector assembly 1&2 in the Git position.

The acceleration condition of operation is obtained by positioning themode selector assembly 162 so that the switch arms of the assembly arein contact with contacts A. In this condition of operation theelectromagnet 72 is constantly energized so long as the vehicle is belowthe speed error sensing range since switch 32 is closed. Switch ass isin a position such that the circuit to electromagnet t is can becompleted by the operator by the closing of switch 193, thus bypassingthe inhibiting switch M4. The pressure in speed warning chamber 56 isatmospheric pressure since valve 92 is seated to close passage 78. Whenthe operator presses knob 21d inwardly to close switch 1%, and holds itin this position, electromagnet is energized. This occurs even thoughthe vehietc may be stopped or at any speed below the speed error sensingrange of the speed transducer 22. Valve 13% is opened by electromagnet146 and engine intake manifold vacuum is introduced into chamber 54.Diaphragm thus moves to the left to open the engine throttle valve 12,causing the vehicle to accelerate. Since switch we is open, the holdingrelay assembly 23?; is not energized and the only holding action formaintaining energization of electromagnet M 6 is the manual holdingaction of the operator keeping switch 193 closed against the force ofspring 212. As the vehicle continues to accelerate it reaches the speederror sensing range and the proportion a1 control action of the valveassembly 88 will cause proportional control pressure to be admitted tospeed warning chamber 5a. This pressure acts on diaphragm $3 inopposition to intake manifold vacuum in chamber 54 and causes thediaphragm 53 to move to the right to the necessary extent formaintaining the set vehicle speed. It also acts on diaphragm 1% to closeswitch 104, thus energizing the holding relay assembly 232 to holdelectromagnet 1 36 energized upon the manual release of knob 2316resulting in the opening of switch B 8. Relay assembly 232 remainsenergized through switch 1% and the sys tem then functions in the speedmaintaining condition of operation until released by opening the brakerelease switch 22-h, the manual release switch or moving the modeselector to the Oil position. Thus this mode of system operation permitsthe vehicle operator to accelcrate from any speed to the desired setspeed and to establish the speed maintaining condition of operation uponattainment of the set speed. When the switch 1% is not closed to obtainacceleration, the system operates in the same manner as in the Normalcondition. A speed warning back pressure will be obtained when thevehicle reaches the desired set speed and the operator may lock thesystem in the speed maintaining condition by pushing knob 21d inwardlyto close switch 193 momentarily while the vehicle is operating in orabove the speed error sensing range.

The Prearm condition of operation differs from the other conditions ofoperation in that when the vehicle is brought up to the preset speed bynormal operation of the accelerator pedal, the system is automaticallyplaced in the speed maintaining condition of operation. This isaccomplished by connecting contact 129 of switch 194 to the source ofelectrical energy through normally closed switch 1% of the operationalcontrol switch assembly 1194 rather than through the normally openswitch 198 of that assembly. When the vehicle reaches the set speed,engine intake manifold vacuum in the servo speed warning chamber 56 actsto close switch 194 and energize the relay assembly 232, putting thesystem in the speed maintaining mode of operation. The operator is notrequired to push knob 216 and the system will automatically shift to thespeed maintaining condition of operation so long as the vehicle is in orabove the speed error sensing range. In order to release the system, theVehicle brakes must be applied to open brake switch 229 and to bring thevehicle to a speed below the speed error sensing range, or knob 216 mustbe pulled to open switch 1% and hold it open until the vehicle speeddrops below the speed error sensing range, or mode selector assembly 162must be set to the Off position.

The Both mode of operation combines the features of the Acceleration andPrearm condition of operation. This permits the operator to accelerateunder power throttle conditions from any speed up to the set speed andthe system will automatically change to the speed maintaining mode ofoperation. If the operator does not use the power acceleration featurebut manually accelerates to the preset speed, the system will shift tothe speed maintaining condition of operation as in the prearm conditionrather than merely giving a speed warning back pressure as occurs in theNormal and Acceleration conditions of operation.

' In the claims:

1. A vehicle road speed warning and control system for a vehicle havinga vehicle engine speed control mechanism, said system comprising,

first means for generating a speed error signal,

second means for moving said vehicle engine speed control mechanismunder power, a third means for manually moving said vehicle engine speedcontrol mechanism,

a source of power for said second means,

fourth means receiving said signal and power from said source fordelivering power to said second means in response to said signal forurging said vehicle engine speed control mechanism toward a decreasingspeed direction,

fifth means receiving power from said source and selectively operable todeliver power to said second means for urging the vehicle engine speedcontrol mechanism toward an increasing speed direction,

first normally open switch means connected to close in in response topower at said second means from said fourth means,

second normally open switch means for electrically bypassing said firstswitch means,

holding means for closing and holding said second switch means closedwhen energized,

mode selector switch means for selectively conditioning selective onesof said means to provide any of a plurality of selective systemconditions, said plurality of selective system conditions comprising atleast an off condition and a system operational condition,

operator controlled switch means for activating the system in at leastone of the plurality of system conditions,

and a source, of electrical energy having one. side connected to saidfirst and fourth means and to said mode selector switch means.

2. The system of claim 1, said mode selector switch means beingpositioned to render said first means inoperative to generate a speederror signal and to render said fifth means inoperative to deliver powerto said second means to condition said system to a mode wherein only 5said third means is capable of moving said vehicle engine speed controlmechanism.

3. The system of claim 1, said mode selector switch means beingpositioned to condition said system to provide a speed warning at adesired vehicle speed by connecting said source of electrical energy toenergize said first means and said fourth means.

4. The system of claim 1, said mode selector switch means beingpositioned to condition said system to provide a speed warning at adesired vehicle speed by connecting said source of electrical energyto-energize said first means to furnish said speed error signal to saidfourth means when the actual vehicle speed approaches the desiredvehicle speed within a limited constant range of vehicle speed.

5. The system of claim 4, said first means being constructed andarranged to generate the speed error signal only when the actual vehiclespeed is within the limited constant range of vehicle speedincluding thedesired vehicle speed to activate said fourth means for the delivery ofsuificient power to said second means to provide the speed warning as aspeed decreasing force delivered to said third means.

6. The system of claim4, said mode selector switch means beingpositioned to condition said system to provide a speed warning at adesired vehicle speed and to condition said operator control switchmeans for changing the speed warning condition of said system to avehicle speed maintaining condition by connecting said source ofelectrical energy to energize said first means and said fourth means.

7. The system of claim 1, being operable to provide a speed warning at adesired vehicle speed,

said mode selector switch means being positioned to connect said sourceof electrical energy to energize said first and fourth means,

said first means commencing to generate the speed error signal when theactual vehicle speed enters a range of vehicle speed including thedesired vehicle speed to activate said fourth means for deliver ofsufficient power to said second means to provide the speed Warning as aspeed decreasing force to said third means.

8. The system of claim 7, being further operable to maintain the actualvehicle speed at the desired vehicle speed'independently of operatoroperation of said third means,

said first switch means being closed by power delivered to said secondmeans by said fourth means,

said operator controlled switch means being connected through said modeselector switch means to said source of electrical energy and operableto energize said fifth means through said first switch means to providepower to said second means for cooperation with power from said fourthmeans to maintain the actual vehicle speed at the desired set speed.

9. The system of claim 8, wherein said holding means is connected to beenergized concurrently with said fifth means 6b to close said secondswitch means to electrically bypass said first switch means, and thefifth means energizing action of said operator controlled switch means ito maintain said fifth means energized,

and means for manually disconnecting said fifth means from said sourceof electrical energy to return said system to a speed warning condition.10. The system of claim 1, said mode selector switch means beingpositioned to condition said system to provide a power accelerationcondition subject to control of said operator control switch means byconnecting said source of electrical energy to energize said first meansand said fourth means and to prearm said fifth means,

said operator control switch means being connected to energize saidfifth means independently of operation of said first switch means.

11. The system of claim 1, said operator controlled switch meansincluding a normally closed switch and a normally open switch,

said mode selector switch means connecting said source of electricalenergy to said normally closed switch and to one contact of saidnormally open switch of said operator controlled switch means andconmeeting said fifth means to the other contact of said normally openswitch means,

said normally open switch being manually closeable to energize saidfifth means to actuate said second means to power accelerate thevehicle.

12. The system of claim 11, said first means generating the speed errorsignal at a predetermined vehicle speed to cause said fourth means todeliver power to said second means as aforesaid to oppose powerdelivered to said second means from said fifth means to prevent poweracceleration of the vehicle at vehicle speeds greater than thepredetermined vehicle speed.

13. The system of claim 12, said mode selector switch means furtherconnecting said holding means to said source of electrical energythrough said first switch means to permit said holding means to closesaid second switch means and connect said fifth means and said holdingmeans to said source of electrical energy independently of furtheropening and closing of said first switch means and said operatorcontrolled switch means normally open switch upon delivery of power tosaid second means by said fourth means to keep said fifth means operableto cause said second means to move said vehicle engine speed controlmechanism to maintain the vehicle speed substantially constant relativeto the predetermined vehicle speed.

14-. The system of claim 1, said mode selector switch means connectingsaid holding means to said source of electrical energy through andsubject to closing of said first switch means and connecting said fifthmeans to said source of electrical energy subject to closing of saidsecond switch means by said holding means to cause said fourth and fifthmeans to deliver power to second means to maintaining a constant vehiclespeed in accordance with said speed error signal when said first switchmeans is closed.

15. A vehicle speed warning and control system comprising:

means generating a speed error signal within a constant range of vehiclespeed including a desired vehicle speed;

vehicle engine speed control mechanism;

servo means for moving said vehicle engine speed control mechanism underpower;

manually operable means and manually moving said vehicle engine speedcontrol mechanism;

a source of servo power;

and control means for said servo receiving servo power from said sourceand said speed error signal,

and selectively operable to permit power acceleration of the vehicle bysaid servo means from a vehicle speed below the constant range ofvehicle speed to the desired vehicle speed,

manual acceleration of the vehicle by said manually operable means,

speed warning of a condition wherein the actual vehicle speed equals thedesired vehicle speed,

and maintenance of the vehicle speed at the desired vehicle speed.

References Cited by the Examiner UNITED STATES PATENTS 2,916,100 12/59Teetor ISO-82.1 3,081,837 3/ 63 Fiteny 82.1 3,087,340 4/63 McMurray etal. 180-82.1 X 3,088,538 5/63 Brennan et al. 180-821 A. HARRY LEVY,Primary Examiner.

1. A VEHICLE ROAD SPEED WARNING AND CONTROL SYSTEM FOR A VEHICLE HAVINGA VEHICLE ENGINE SPEED CONTROL MECHANISM, SAID SYSTEM COMPRISING, FIRSTMEANS FOR GENERATING A SPEED ERROR SIGNAL, SECOND MEANS FOR MOVING SAIDVEHICLE ENGINE SPEED CONTROL MECHANISM UNDER POWER, THIRD MEANS FORMANUALLY MOVING SAID VEHICLE ENGINE SPEED CONTROL MECHANISM, A SOURCE OFPOWER FOR SAID SECOND MEANS, FOURTH MEANS RECEIVING SAID SIGNAL ANDPOWER FROM SAID SOURCE FOR DELIVERING POWER TO SAID SECOND MEANS INRESPONSE TO SAID SIGNAL FOR URGING SAID VEHICLE ENGINE SPEED CONTROLMECHANISM TOWARD A DECREASING SPEED DIRECTION, FIFTH MEANS RECEIVINGPOWER FROM SAID SOURCE AND SELECTIVELY OPERABLE TO DELIVER POWER TO SAIDSECOND MEANS FOR URGING THE VEHICLE ENGINE SPEED CONTROL MECHANISMTOWARD AN INCREASING SPEED DIRECTION, FIRST NORMALLY OPEN SWITCH MEANSCONNECTED TO CLOSE IN IN RESPONSE TO POWER AT SAID SECOND MEANS FROMSAID FOURTH MEANS, SECOND NORMALLY OPEN SWITCH MEANS FOR ELECTRICALLYBYPASSING SAID FIRST SWITCH MEANS, HOLDING MEANS FOR CLOSING AND HOLDINGSAID SECOND SWITCH MEANS CLOSED WHEN ENERGIZED, MODE SELECTOR SWITCHMANS FOR SELECTIVELY CONDITIONING SELECTIVE ONES OF SAID MEANS TOPROVIDE ANY OF A PLURLAITY OF SELECTIVE SYSTEM CONDITIONS, SAIDPLURALITY OF SELECTIVE SYSTEM CONDITIONS COMPRISING AT LEAST AN "OFF"CONDITION AND A SYSTEM OPERATIONAL CONDITION, OPERATOR CONTROLLED SWITCHMEANS FOR ACTIVATING THE SYSTEM IN AT LEAST ONE OF THE PLURALITY OFSYSTEM CONDITIONS, AND A SOURCE OF ELECTRICAL ENERGY HAVING ONE SIDECONNECTED TO SAID FIRST AND DOURTH MEANS AND TO SAID MODE SELECTORSWITCH MEANS.